Best Practices For RAP And RAS Management
Quality Improvement Series 129Best Practices forRAP and RASManagement
This publication is provided by the Members of the National Asphalt Pavement Association (NAPA), whoare the nation’s leading asphalt producer/contractor firms and those furnishing equipment and servicesfor the construction of quality asphalt pavements.NAPA Members are dedicated to providing the highest quality asphalt paving materials and pavements,and to increasing the knowledge of quality asphalt pavement design, construction, maintenance andrehabilitation. NAPA also strongly supports the development and dissemination of research, engineeringand educational information that meets America’s needs in transportation, recreational, and environmentalpavements.NAPA Building 5100 Forbes Blvd. Lanham, MD 20706-4407Tel: 301-731-4748 Fax: 301-731-4621 Toll free 1-888-468-6499www.AsphaltPavement.org NAPA@AsphaltPavement.orgMike AcottPresidentT. Carter RossVice President for CommunicationsThis publication is designed to provide information of interest to NAPA Members and is not to beconsidered a publication of standards or regulations. The views of the authors expressed herein donot necessarily reflect the decision making process of NAPA with regard to advice or opinions onthe merits of certain processes, procedures, or equipment.COPYRIGHT NOTICEPublications produced and published by the National Asphalt Pavement Association (NAPA) are copyrighted by the Association and may not be republished or copied (including mechanical reproductions)without written consent. To obtain this consent contact the Association at the address given above. 2015 National Asphalt Pavement AssociationQuality Improvement Series 129Printed 12/15
Quality Improvement Series 129Best PracticesforRAP and RASManagementByRandy C. West, Ph.D., P.E.DirectorNational Center for Asphalt TechnologyAuburn UniversityNATIONAL ASPHALTPAVEMENT ASSOCIATIONNAPA Building 5100 Forbes Blvd. Lanham, MD 20706-4407Tel: 301-731-4748 Fax: 301-731-4621 Toll free 1-888-468-6499www.AsphaltPavement.org NAPA@AsphaltPavement.orgNATIONAL ASPHALT PAVEMENT ASSOCIATION QIP 129Best Practices for RAP and RAS Management3
Technical Report Documentation Page1. Report No.QIP 1292. Government Accession No.4. Title and SubtitleBest Practices for RAP And RAS Management3. Recipient’s Catalog No.5. Report DateDecember 20156. Performing Organization Code7. Author(s)Randy C. West, Ph.D., P.E.8. Performing Organization Report No.QIP 1299. Performing Organization Name and AddressNational Asphalt Pavement Association5100 Forbes Blvd.Lanham, MD 2070610. Work Unit No. (TRAIS)12. Sponsoring Organization Name and AddressFederal Highway AdministrationOffice of Asset Management, Pavement and Construction1200 New Jersey Ave. SEWashington, DC 2059013. Type of Report and Period CoveredFinal Report11. Contract or Grant No.DTFH61-13-H-0002714. Sponsoring Agency CodeFHWA-HIAP-2015. Supplementary NotesThis project was funded under FHWA Cooperative Agreement DTFH61-13-H-00027 “Deployment of Innovative Asphalt Technologies.”16. AbstractThis document covers the current best practices for management of reclaimed asphalt pavement (RAP) and reclaimed asphalt shingles(RAS) as of 2015. The goal of this guide is to facilitate the most effective utilization of RAP as a component in asphalt paving mixtures. Thisdocument provides guidance for management of RAP from the time of collection through processing, sampling and testing of RAP for mixdesign, and quality control practices during production of asphalt mixtures containing RAP. A brief section also presents best practices formanagement of RAS for use in asphalt paving mixtures. Good RAP and RAS management practices are important to ensure the greatesteconomic benefit of these materials and the highest quality asphalt mixtures.17. Key WordsReclaimed Asphalt Pavement, RAP, Reclaimed Asphalt Shingles, RAS,Asphalt Pavements, Quality Management18. Distribution StatementNo restrictions.19. Security Classification(of this report)Unclassified.21. No. of Pages4420. Security Classification(of this page)Unclassified.Form DOT F 1700.7 (8-72)4Best Practices for RAP and RAS Management22. PriceNAReproduction of completed page authorizedNATIONAL ASPHALT PAVEMENT ASSOCIATION QIP 129
CONTENTSIntroduction.7Historical Perspective on Recycling.7Purpose of this Guide.8Chapter 1: Managing the Reclaiming Process.9Milling.9Selecting the Milling Depth.10Inspecting the Milling Process.10Aggregate Breakdown During Milling.11Milling for Removal of Specific Layers.12Pavement Demolition.12Plant Waste.13Contamination.14Chapter 2: Inventory Management and Processing RAP.15Inventory Analysis.15Single or Multiple Unprocessed RAP Stockpiles.17Captive or Continuously Replenishing RAP Stockpiles.17Processing and Crushing RAP.18Processing Millings.19Millings: Recommended Processing Options.19Processing RAP from Multiple Sources.20Screening RAP During Processing.21Crusher Types.21Weather.22Fractionating.22Moving the Processed RAP Stockpiles.24Stockpiling to Minimize Segregation.24Stockpiling to Minimize Moisture.24In-line RAP Crushers or Crusher Circuits.25Advantages and Disadvantages of Different RAP Processing Options.26Chapter 3: Sampling and Testing the RAP.27RAP Variability.27Sampling and Testing Frequency.27Sampling Method.28Test Methods.29Methods for Determining RAP Asphalt Contents andRecovering Aggregates for Characterization.30Ignition Method.30Solvent Extraction.30Aggregate Bulk Specific Gravity.31Chapter 4: Production Concerns for Mixes Containing RAP.33Chapter 5: Management of Recycled Asphalt Shingles.35Background.35Composition and Types of RAS.35Specifications.36Processing RAS.36Stockpiling.37Blending RAS with Other Materials.37Sampling and Testing.37Mix Production.38Chapter 6: Summary and Conclusions.39References.41NATIONAL ASPHALT PAVEMENT ASSOCIATION QIP 129Best Practices for RAP and RAS Management5
NoticeThis document is disseminated under the sponsorship of the U.S. Department of Transportation in the interest of information exchange. The U.S. Government assumes no liability forthe use of the information contained in this document.The U.S. Government does not endorse products or manufacturers. Trademarks or manufacturers’ names appear in this report only because they are considered essential to theobjective of the document.Quality Assurance StatementThe Federal Highway Administration (FHWA) provides high-quality information to serve government, industry, and the public in a manner that promotes public understanding. Standardsand policies are used to ensure and maximize the quality, objectivity, utility, and integrityof its information. FHWA periodically reviews quality issues and adjusts its programs andprocesses to ensure continuous quality improvement.6Best Practices for RAP and RAS ManagementNATIONAL ASPHALT PAVEMENT ASSOCIATION QIP 129
IntroductionHistorical Perspective on RecyclingThe asphalt paving industry has had great success with recycling asphalt pavements.Other recycled materials such as shingles, slag, ground tire rubber, glass, and cellulosefibers produced from recycled paper have also been used in numerous asphalt projects fordecades. Recycling of asphalt pavements dates back to 1915 (Kandhal & Mallick, 1997),but it did not become a common practice until the early 1970s when asphalt binder pricesskyrocketed as a result of the 1973 Arab Oil Embargo. The asphalt paving industry reactedto this situation by developing recycling technologies that helped reduce the demand onasphalt binder and thereby reduce the costs of asphalt paving mixtures. Many practicesinitially developed during that period are still in use today and have become part of routineoperations for pavement construction and rehabilitation.Motivations for recycling include economic savings and environmental benefits. Recycling reduces the demand for non-renewable natural resources (both asphalt and aggregates) and thereby also reduces the energy and emissions associated with the extractionand transportation of those raw virgin materials. Recycling also avoids landfilling of oldpavement materials removed during rehabilitation. The economic benefit results frommaterials cost savings resulting from a replacement of a portion of virgin aggregates andbinders. The asphalt and aggregate components of an asphalt mix represent the greatestproportion of the cost of pavement construction (Copeland, 2011).For more than three decades, two guiding principles of asphalt recycling have been: 1)mixtures containing RAP should meet the same requirements as mixes with all virgin materials, and 2) mixes containing RAP should perform equal to or better than virgin mixtures.Recent NAPA surveys of the asphalt pavement industry have reported that across theU.S., the average RAP content in new asphalt mixes has steadily increased in recentyears with the national average RAP content now around 20%. However, the percentageof RAP used in new plant mix varies considerably by state (Hansen & Copeland, 2015).Quality recycled mixes have been successfully designed and produced for many years.The proof is in performance: a recent study comparing the performance of recycled versusvirgin mixes based on Long-Term Pavement Performance (LTPP) data from 16 U.S. statesand two Canadian provinces shows that overlays containing at least 30% RAP performedequal to overlays using virgin mixtures (Carvalho et al., 2010; West et al., 2011). At theNCAT Test Track, test sections containing 50% RAP using standard Superpave mix designprocedures for each layer outperformed companion test sections with all virgin materialsin all pavement performance measures through five years of heavy loading (West et al.,2012; Timm et al., 2016).NATIONAL ASPHALT PAVEMENT ASSOCIATION QIP 129Best Practices for RAP and RAS Management7
Purpose of This GuideThe goal of this best management practices guide is to facilitate the most effectiveutilization of RAP as a component in an asphalt paving mixture. This document providesguidance for management of reclaimed asphalt pavement (RAP) materials from the time ofcollection through processing, mix design, and quality control practices during productionof asphalt mixtures containing RAP. Good RAP management practices are important toensure the greatest economic benefit for RAP and the highest quality of recycled asphaltmixtures.This document is organized to follow the sequence of handling and evaluating RAPmaterials from the point of reclaiming RAP through quality control practices during production of asphalt mixtures containing RAP. Chapter 1 provides guidance on reclamationprocesses. Chapter 2 covers decisions and practices for processing and inventory management of RAP materials. Chapter 3 presents best practices for sampling and testingstockpiled RAP materials. Chapter 4 discusses production concerns for mixes containingRAP. Chapter 5 provides additional guidance on best practices for handling ReclaimedAsphalt Shingles (RAS).This document represents the current best practices for RAP and RAS managementas of 2015 and, as such, may need periodic revision. This document was prepared by theNational Center for Asphalt Technology and reviewed by numerous agency and industryexperts.8Best Practices for RAP and RAS ManagementNATIONAL ASPHALT PAVEMENT ASSOCIATION QIP 129
1RAP may be obtained from several sources. The mostcommon method is through pavement milling operations, also known as cold planing. Two other commonsources of RAP are full-depth pavement demolitionand wasted asphalt plant mix. This chapter discussesthese different types of RAP sources.MillingMilling is a beneficial part of pavement rehabilitation. Advantages of milling include the following: Removes distressed pavement layers,maintains clearances under bridges, andavoids buildup of pavement weight on bridges;Managing theReclaiming Process Avoids filling up curbs and avoids drop-offs atdrainage inlets in urban settings; Reduces the need for the costly addition ofshoulder material along the edge of pavements on rural roadways; Restores pavement grades, cross-slopes, andprofiles, which are important for smoothness; Leaves a rough texture on the remainingsurface that creates a very good bond with anoverlay; and Is an efficient removal process that can bedone within a short lane-closure with thepaving operations.Figure 1-1. Milling machine removes asphalt pavement layers as part of pavement rehabilitation.(Photo courtesy of Astec Industries)NATIONAL ASPHALT PAVEMENT ASSOCIATION QIP 129Best Practices for RAP and RAS Management9
Selecting the Milling DepthSelection of the milling depth is a critical agencydecision during planning of the rehabilitation of apavement. Milling depth should be based on visual examination of cores to determine the depthof surface cracks and/or the location of weak layersor interfaces. Removal of these distressed or weaklayers helps achieve long-term performance of theoverlay. Cores should be taken at least once everylane mile on highways and one per lane per block oncity streets. It is important to check the cross-sectionof pavement layers across lanes, since roads haveoften been widened in the past with a different buildupon the added roadway width.Figure 1-2. Roadway cores showing distressedlayers: top-down cracking on top; strippingdamage on the bottom.10Best Practices for RAP and RAS ManagementIn cases where milling is also used to improve theroadway’s profile (smoothness) and/or cross-slope,it must be realized that the milling depth will vary.Careful consideration must be given to how the variable thickness may affect the structural integrity ofthe remaining pavement as well as the uniformity ofthe milled material.Inspecting the Milling ProcessMilling processes should be closely examined tomake sure the milled material is not contaminatedwith soil, base material, paving geotextiles, or otherdebris. This is particularly important for deep millsor milling on shoulders or widened roadways. Milledmaterials that become contaminated should be usedonly as shoulder material and should be stockpiledseparately from RAP that will be used in asphalt mix.A recommended maximum limit of 1% deleteriousmaterial should be used to evaluate RAP contamination. This limit is consistent with requirements forvirgin aggregates.The milled surface should also be inspected for“scabbing” where thin, weakly bonded layers areleft in place. Figure 1-3 shows an example of amilled pavement with scabbing. If this is observed,the milling depth should be adjusted to remove thescab layer. If such a weakly bonded layer is allowedto remain in place, the performance of the overlaywill severely diminish.Finally, the milled surface should be inspected foruniform texture. A non-uniform texture resulting fromworn or broken tips on the milling drum can causeproblems with compaction of thin overlays. It mayalso cause an unsafe surface for motorcycles if themilled surface is opened to traffic. Some agenciesrequire a simple texture check and have a limit ofZ\x-inch peak to valley on the milled surface.NATIONAL ASPHALT PAVEMENT ASSOCIATION QIP 129
Figure 1-3. Milled pavement surface with thin scab layer that will likely lead to premature failure of theoverlay. (Photo courtesy of Jim Scherocman)Aggregate Breakdown During MillingMilling machines consume a lot of energy inremoving pavement layers by impacting the pavement with milling teeth mounted on a drum rotatingat about 200 rpm. The impacts break up the pavement by ripping through the mastic and aggregateparticles. Crushing of aggregate particles causesthe gradation of the millings to be much finer thanthe gradation of the pavement layers in place. In thepast, pavement cores were obtained before millingNATIONAL ASPHALT PAVEMENT ASSOCIATION QIP 129and the layers to be milled were removed for extraction tests. Adjustment factors were then applied tothe extracted gradation to estimate the gradationafter milling. However, this technique is not reliablesince the amount of aggregate degradation dependson the hardness and brittleness (impact resistance)of the aggregate, the stiffness of the asphalt (and,therefore, the temperature of the pavement at thetime of milling), the speed of the milling machine, andthe depth of the cut.Best Practices for RAP and RAS Management11
Milling for Removal of Specific LayersIn some cases, it may be advantageous to usespecial milling operations to remove specific pavement layers. One example is milling to remove anopen-graded friction course layer or chip seal thatis raveling. If the pavement will be resurfaced with anew OGFC or other type of very thin wearing course,it may be beneficial to remove only the existing OGFCsurface without milling much into the underlying layerand produce a fine-textured milled surface on whichthe new surface course can be placed. In this case,a micro-milling drum, as shown in Figure 1-4, canprovide a much smoother surface texture which isbetter suited for achieving the desired smoothnessfor the new surface layer. Using a normal milling drummay result in deep and/or irregular groves that canlead to dragging when a thin layer is placed on top.surface layer separately from the underlying layersinclude projects with surface layers containing steelslag or asphalt-rubber binder. High specific gravitysteel slag can introduce significant variations in RAPstockpiles. Similarly, it may be challenging to recycleRAP with high rubber contents, so keeping that material separated from the other RAP may be a RAPmanagement consideration.Pavement DemolitionRAP may also be obtained from utility cuts in aroadway, removal of isolated areas for patching,or complete demolition of an existing pavementusing a bulldozer or backhoe. Figure 1-5 shows anexample of pavement rubble resulting from demolition of a roadway. This process is typically limitedto small areas of pavement. This method of pave-Figure 1-4. Micro-milling drums have three times the number of teeth as a normal milling drum.A special milling operation may also be beneficialwhen it is desirable to mill the surface layer in onepass and the underlying layer(s) in a second passbecause the surface layer contains a high-valuefriction aggregate, a very high specific gravity aggregate, and/or a modified binder. Some contractorshave found the two-pass milling operation to beeconomical when the cost of new friction aggregatesis very high and the project specifications allow thesurface-course RAP to be used in new surface layers. Other situations that may warrant milling the12Best Practices for RAP and RAS Managementment removal is slow and results in large chunks ofpavement rubble that may be more challenging toprocess into a usable recycled material. It is important that the quality of this type of material be closelymonitored during unloading to avoid contaminationand deleterious materials, particularly when it isreceived from another contractor. When pavementrubble is contaminated with underlying layers andsoil, it is better for this material to be crushed andused as a shoulder or base material than used inan asphalt mixture.NATIONAL ASPHALT PAVEMENT ASSOCIATION QIP 129
Figure 1-5. Pavement rubble from full-depth demolition of a roadway.Plant WasteAll asphalt plant operations generate some material waste during plant start-up, transition betweenmixes, and clean-out. Generally, start-up and shutdown plant wastes have very low asphalt contents.Another form of waste is mix rejected from a projectdue to incomplete coating or due to the mix temperature being too high or too low for the job. Othersituations that may result in wasted mix include trucksloaded with too much mix to finish the job or mixthat could not be placed due to inclement weather.These waste materials are often stockpiled for laterprocessing into a recyclable material.NATIONAL ASPHALT PAVEMENT ASSOCIATION QIP 129Because these waste mixes have not been subjected to environmental aging from years of service,the asphalt binder is less aged than RAP recoveredfrom the road. Waste materials also have fewer finesthan other sources of RAP as it was not milled orbroken up during demolition. However, waste materials must be thoroughly mixed and processed tomake them into uniform, recyclable materials. Wastematerials are often combined with other sources ofRAP in multiple-source stockpiles. Processing RAPfrom multiple sources is discussed in greater detailin Chapter 2.Best Practices for RAP and RAS Management13
ContaminationIt is important that stockpiles be kept free ofcontaminants from the beginning. It is easy to understand how bad perceptions of RAP may formwhen there is dirt, rubbish, or vegetation in RAPstockpiles, or when trash is found in the mix when itshows up on the job site or pops out of the pavementa few days after paving. Treat RAP stockpiles as themost valuable material on the plant yard—becausethey are. Truck drivers bringing recyclable materialsonto the plant yard must be clearly instructed whereto dump loads of RAP or pavement rubble so thatunwanted construction debris does not end up inthe RAP stockpile. Drivers must also be instructedto clean the truck beds before hauling millings orusable RAP. The plant QC personnel and the loaderoperator should also regularly inspect unprocessedand processed RAP stockpiles to make sure they donot contain deleterious materials. If contaminantsare found, dig them out immediately so that theyare not covered up with other RAP brought ontothe yard.Figure 1-6. Multiple-source RAP pile with dirt contamination (circled in red).14Best Practices for RAP and RAS ManagementNATIONAL ASPHALT PAVEMENT ASSOCIATION QIP 129
2Inventory Managementand Processing RAPPoor management of RAP stockpiles is commonlycited as a reason agencies are reluctant to increaseallowable RAP contents in asphalt mixtures. Thischapter provides guidance on inventory management of RAP materials and options for stockpiling,crushing, and screening RAP. Good materials management practices should always be a part of thequality control program for any asphalt mix production operation. For production of quality mixes withhigh RAP contents, excellent materials managementpractices are essential.Inventory AnalysisRAP management should begin with a basic inventory analysis of available RAP and mix production.This analysis is important to establish realistic goalsfor how much RAP can be used at a particular plant.The analysis includes four simple steps:1. An inventory of RAP on hand and RAPgenerated per year;2. A summary of mixes produced per yearby mix types and customers;3. Determining the maximum amount of RAPthat can be used; and4. A comparison of the quantity of RAPavailable to the amount of RAP needed.Note that in this context, “RAP contents” referto the RAP material as a percentage of the totalmixture. Some agencies now have specificationlimitations based on the percentage of RAP binderin the total binder content. Such specifications havemerit when dealing with changing the grade of thevirgin binder in the recycled mixture. However, foran inventory analysis, the more common expressionof RAP content as a percentage of the total mixtureis more appropriate.Examples are the best way to illustrate the inventory analysis. Three cases are presented.Case #1: Contractor A has an estimated 20,000 tons of RAP on a plant site and typically brings in about30,000 tons per year from milling projects and other sources. The plant typically produces about 150,000tons of HMA per year. Of that quantity, approximately 100,000 tons is produced for state projects, andthe other 50,000 tons is produced for commercial work and local governments.The contractor generally follows DOT specifications for designing mixes for local and commercial work.It is estimated that 80% of the mix produced is surface mix. The state specifications currently allow upto 20% RAP in surface mixes and up to 30% in base and binder layer mixes. Contractor A currently usesthe maximum-allowable RAP by specification. RAP Available 20,000 tons 30,000 tons 50,000 tons Maximum RAP Needed 150,000 tons [(80% surface 20% RAP) (20% base/binder mix 30% RAP)] 33,000 tons of RAPTherefore, for Contractor A to increase RAP usage, they will have to either1. Get the agency specifications changed;2. Increase the plant’s annual production; or3. Increase RAP contents in local and commercial work.If Contractor A does nothing different, they will have a large excess supply of RAP, which may becomea storage problem.NATIONAL ASPHALT PAVEMENT ASSOCIATION QIP 129Best Practices for RAP and RAS Management15
Case #2: Contractor B h
NATIONAL ASPHALT PAVEMENT ASSOCIATION QIP 129 . Best Practices for RAP and RAS Management . 3. Quality Improvement Series 129. Best Practices. for RAP and RAS. Management. NATIONAL ASPHALT PAVEMENT ASSOCIATION. NAPA Building 5100 Forbes Blvd. Lanham, MD 20706-4407 Tel: 301-731-4748 Fax: 301-731-4621 Toll free 1-888-468-6499
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